1. Field of the invention
This invention relates to apparatus for reading out a stationary optical memory, in which a light source is associated with each character, all characters being imaged by optical elements to a common location.
Systems like this are used for fast character reading for photographic type composition apparatus or information retrieval systems for computers.
Known techniques employed in the field of high speed printing involve selecting characters to be printed from a given font. The selection process may, for example, include deflecting an optical beam to the location of a character and projecting an image of the selected character onto a suitable recording medium.
2. Description of prior art
An arrangement like this is described in German patent publication 2 342 412. The characters to be projected are illuminated by flash lamps. Each character is associated with a lens, the characters being arranged at the focal point of the lenses in order to collimate the beams emerging from the characters. A concave mirror is used to de-collimate the parallel rays and project their image through the center of the optical matrix. Therefore a special optical matrix is necessary bearing no characters in its center.
In addition, in spite of the collimated beams, the quality of the images of marginal characters is poor as compared to images of characters located near the optical axis.